add unit test and fix lint

packages/next/src/lib/metadata/resolve-metadata.test.ts

@@ -0,0 +1,37 @@
+import { accumulateMetadata, MetadataItems } from './resolve-metadata'
+
+describe('accumulateMetadata', () => {
+  describe('merge title', () => {
+    it('should merge page title', async () => {
+      const metadataItems: MetadataItems = [
+        [{ title: 'root' }, null],
+        [{ title: 'layout' }, null],
+        [{ title: 'page' }, null],
+      ]
+      const metadata = await accumulateMetadata(metadataItems)
+      expect(metadata).toMatchObject({
+        title: { absolute: 'page', template: null },
+      })
+    })
+
+    it('should merge page title', async () => {
+      const metadataItems: MetadataItems = [
+        [{ title: 'root' }, null],
+        [
+          { title: { absolute: 'layout', template: '1st parent layout %s' } },
+          null,
+        ],
+        [
+          { title: { absolute: 'layout', template: '2nd parent layout %s' } },
+          null,
+        ],
+        [null, null], // same level layout
+        [{ title: 'page' }, null],
+      ]
+      const metadata = await accumulateMetadata(metadataItems)
+      expect(metadata).toMatchObject({
+        title: { absolute: '2nd parent layout page', template: null },
+      })
+    })
+  })
+})

packages/next/src/lib/metadata/resolve-metadata.ts

@@ -3,7 +3,6 @@ import type {
   ResolvedMetadata,
   ResolvingMetadata,
 } from './types/metadata-interface'
-import type { AbsoluteTemplateString } from './types/metadata-types'
 import type { MetadataImageModule } from '../../build/webpack/loaders/metadata/types'
 import { createDefaultMetadata } from './default-metadata'
 import { resolveOpenGraph, resolveTwitter } from './resolvers/resolve-opengraph'

packages/next/src/lib/metadata/resolvers/resolve-title.test.ts

@@ -0,0 +1,22 @@
+import { resolveTitle } from './resolve-title'
+
+describe('resolveTitle', () => {
+  it('should resolve nullable template as empty string title', () => {
+    expect(resolveTitle('', null)).toEqual({ absolute: '', template: null })
+    expect(resolveTitle(null, null)).toEqual({ absolute: '', template: null })
+  })
+
+  it('should resolve title with template', () => {
+    // returned template should equal the input title's template
+    expect(resolveTitle('title', 'dash %s')).toEqual({
+      absolute: 'dash title',
+      template: null,
+    })
+    expect(
+      resolveTitle({ default: 'title', template: '%s | absolute' }, 'dash %s')
+    ).toEqual({ absolute: 'dash title', template: '%s | absolute' })
+    expect(
+      resolveTitle({ default: '', template: '%s | absolute' }, 'fake template')
+    ).toEqual({ absolute: 'fake template', template: '%s | absolute' })
+  })
+})